Ultrashortpulse light source from terahertz to the extreme ultraviolet

• Subject Area: Condensed Matter Physics
• Term: Funded in 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 565409669

In recent years, ultrafast time-resolved spectroscopy methods have benefited enormously from being able to tune both the pump wavelength and the sample wavelength in the experiment. This applies both to frequency conversion in the purely visible range and, in recent years, increasingly to conversion in the long-wave terahertz and short-wave extreme ultraviolet range. For the further development of our working group, we would like to set up a new short-pulse laser system that allows pump and probe combinations both in the visible spectral range and in the combination of terahertz and visible up to terahertz pump and extreme ultraviolet probe. These combinations enable us to carry out our current (SFB1073: projects A02, B07, B10; SFB1456, project B01), newly started (SFB1633: project C01) and planned (e.g. SFB initiative Göttingen, SFB initiative Marburg) scientific research in the field of energy conversion at interfaces and to further develop it methodologically. In addition, the new ultrashort pulsed laser system will enable us to significantly improve the existing time-resolved optical spectroscopy and, in particular, to establish new THz pump/probe experiments in the field of dynamics in transition metal dichalcogenide heterostructures in our group. Finally, with the new setup we would like to expand our research field into the recently started THz-ARPES area ‘lightwave electronics’. In particular, we are aiming not only to excite the samples with THz pulses, but also to image the entire band structure dynamics with photoemission momentum microscopy using ultrashort extreme ultraviolet light pulses. In order to fulfil the requirements described above, the short-pulse laser system must have the following properties: A femtosecond laser amplifier with pulse repetition rates in the range of single-shot operation up to hundreds of kilohertz with simultaneously high pulse energy (hundreds of microjoules) and high average power (approx. 200 W) is required. This laser system also requires pulse compression to provide femtosecond pulses in the sub-40 fs range with sufficient energy. These pulses are used to simultaneously achieve (i) femtosecond pump-probe spectroscopy, (ii) generation of higher harmonics in the extreme ultraviolet range for the probe pulse and (iii) frequency conversion of the pump pulse using an optical parametric amplifier (OPA). Differential frequency generation between the fundamental of the short pulse laser system and the idler of the OPA is used to provide THz light.

• DFG Programme: Major Research Instrumentation
• Major Instrumentation: Ultrakurzpuls-Lichtquelle: vom Terahertz- bis zum extremen Ultraviolettbereich
• Instrumentation Group: 5700 Festkörper-Laser
• Applicant Institution: Georg-August-Universität Göttingen
• Leader: Professor Dr. Stefan Mathias